The invention relates in general to a coupling mechanism and, more particularly, to a device, for connecting a plunger to a connecting rod, of the type in which a crosshead is connected to the connecting rod, the crosshead having a coupling element with a flange, and a coupling nut mounted to the flange.
A ceramic plunger having a central tapped hole has been used in known devices operating under high and extremely high pressure conditions. The threaded core of a multipart plunger support is screwed in this tapped hold and an adhesive lining is interposed therebetween to prevent rotation. The plunger support has a flange, non-rotatably secured to the threaded core, that is provided with an external thread for receiving a coupling nut carried on the crosshead of the associated connecting rod. In this prior art construction, the plunger support disadvantageously tends to become loosened from the plunger, which is designed as a sleeve, since the adhesive lining is not quite capable of preventing rotation. This causes disengagement between the threaded or contact surfaces of the plunger and the threaded core. Under load, such disengagements ultimately result in a destruction of the plunger. In addition, the screw connection of the threaded core within the tapped hold may easily cause cracking inside the sleeve-like plunger, due to extension forces. Also, the contact areas between the plunger and the plunger support are relatively small so that there is a risk that the ceramic plunger might break even prior to achieving rated operational load. The invention provides a remedy.